The Health Department said the decrease accounted for cases cleared over the past five days and coincided with the high number of cases in recent weeks.

Professor Cheng said Victoria would not transition to lower level restrictions until we saw daily new cases in the "single digits or even low double digits".

"That's a discussion that we're having over the next week or so," he said.

"I won't give you a figure, but single digits or even low double digits. But it does also depend on, you know, if there are mystery cases, then we would worry more about those."

There were 3784 mystery cases on Thursday but 33 new cases was the smallest increase in infections with unknown sources since July 25.

Asked if we was frustrated by the fact new cases numbers are stubbornly hanging around the low 200s mark, Professor Cheng said he was focused on the overall downward trend.

"Numbers go up and down. It's the long-term trends that I'm looking for. You know, we're hopeful – by next week – they'll continue to go down.

"Whether there's a bit of wobble in it – 240, 220 – I'm not so worried about. But I would like to see, over a number of days, that it continues to come down."

Victoria recorded 240 new cases of the virus on Thursday, the fifth consecutive day of less than 300 new infections but higher than Wednesday's total of 216.

There were 13 more deaths, bringing the state toll to 376.

Asked about Melbourne's 8pm to 5am curfew, Premier Daniel Andrews said it was too soon to predict when it would be lifted, but it would not be in place any longer than the government deemed necessary.

Melbourne hits the halfway point on its six-week, stage four lockdown, on Sunday.

"We just can't extrapolate from that data where we're going to be in a week's time, where we're going to be in three weeks' time, four, five weeks' time. It's just really difficult to know," Mr Andrews said.

"If something like the curfew was deemed to be no longer necessary, then it will come off. It won't be imposed for any longer than it needs to be. That's the rule we've tried to apply to all different restrictions we've put in place.

"We've just got to, I think, accept – as tough as it is – that we've still got a long way to go in this and we have to keep, all of us, doing everything we possibly can to drive those numbers down and down further."

Of the 13 deaths recorded on Thursday, eight were linked to aged care.

There are 622 Victorians in hospital, including 43 in intensive care and 28 on a ventilator.

The number of active cases in healthcare workers also dropped from 1065 to 753. Active cases linked with aged care outbreak dropped by 229 to 1811.

The Age's analysis of Department of Health and Human Services data found that in three-quarters of the postcodes that had at least one active case last week, there had been a drop in the number of active cases.

Only 46 postcodes recorded a net increase in active cases compared with one week ago.

Postcode 3021 (Albanvale, Keelba, Kings Park and St Albans) recorded the biggest drop in active cases over the past week.

There are currently 119 active cases in this area, more than half the 304 active cases there last week. However, this area still has a higher infection rate than other parts of Melbourne.

With Craig Butt